Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41N—PRINTING PLATES OR FOILS; MATERIALS FOR SURFACES USED IN PRINTING MACHINES FOR PRINTING, INKING, DAMPING, OR THE LIKE; PREPARING SUCH SURFACES FOR USE AND CONSERVING THEM
  • B41N3/00—Preparing for use and conserving printing surfaces
  • B41N3/03—Chemical or electrical pretreatment
  • B41N3/034—Chemical or electrical pretreatment characterised by the electrochemical treatment of the aluminum support, e.g. anodisation, electro-graining; Sealing of the anodised layer; Treatment of the anodic layer with inorganic compounds; Colouring of the anodic layer

Definitions

• the invention relates to a process for the production of planographic printing plates from roughened, anodized and hydrophilized planographic printing plates, which are coated, exposed to radiation and developed in an aqueous alkaline solution, and planographic printing plates produced thereafter.
• Aluminum substrates in the form of strips, plates or foils, which are provided with positive or negative working radiation-sensitive coatings, are used as presensitized planographic printing plates.
• these coatings contain polymers with functional units which ensure the development of the coatings in the aqueous alkaline developer solutions after imagewise exposure and, if appropriate, further processing steps such as tempering or concreting.
• functional units are -COOH, -SO3H, -PO3H2, -SH, -OH and -NH2.
• the developer solutions generally contain alkali silicates as alkaline components.
• Silicates have the advantage that they attack the Al2O3 layer of the carrier surface built up in the anodizing step significantly less than other alkaline agents.
• the object of the invention is to improve a method of the type described in the introduction in such a way that the degradation of the oxide coating on the front and back of the aluminum carrier and the consequent contamination of the printing forms and of the development devices are avoided or effectively reduced.
• planographic printing plate is treated with a salt solution of a divalent or polyvalent cation in a concentration of at least 0.02 mol / l after the hydrophilization.
• Cation concentrations below 0.02 mol / l - such as those found in hard water - do not show sufficient effectiveness in improving the alkali stability of the anodized layer.
• the preferred concentration range is between 0.04 and 0.4 mol / l.
• the divalent or trivalent ions of the elements of the 2nd and 3rd main group and the 3rd subgroup of the periodic table are particularly suitable cations.
• the divalent and trivalent cations of V, Cr, Mn, Fe, Co, Ni, Zn, Sn and Pb also show good effectiveness.
• both inorganic and organic, mono- and polyvalent anions are suitable as anions, the choice being determined in particular by the solubility of the corresponding salts.
• the treatment of the back of the aluminum support with the salt solution is preferably carried out at a temperature between 20 and 90 ° C in times between 1 second and 1 minute.
• the application of the salt solution is carried out using the usual techniques, eg. B. spraying, rinsing or dipping, easiest after hydrophilizing the front and before applying the light-sensitive coating.
• the back can also be rinsed after the photosensitive coating has been applied. Drying after treatment with the salt solution at temperatures between 50 and 250 ° C can be advantageous.
• planographic printing plates produced by the process according to the invention are distinguished in that the aluminum support of the planographic printing plate is coated with a copy lacquer film and that the copy lacquer film is formed by drying a copy lacquer solution.
• the design of further planographic printing forms according to the invention results from claims 18 to 20.
• the advantage of the process and the planographic printing plates produced thereafter is that the treatment with the salt solution prevents the attack of the aqueous alkaline developer solution on the oxide layer on the front and back of the carrier material.
• the copy varnish solution contains the following components: 5.00% by weight cresol-formaldehyde novolak resin with a hydroxyl number of 420 according to DIN 53783/53240 and a molecular weight (Mw) according to GPC of 10,000 (polystyrene standard), 1.20% by weight of the esterification product of 3 mol of 1,2-naphthoquinone-2-diazide-5-sulfonyl chloride and 1 mol of 2,3,4-trihydroxy-benzophenone, 0.15% by weight of 1,2-naphthoquinone -2-dazid-4-sulfonyl chloride, 0.05% by weight victoria pure blue (CI 44045) and ad 100 wt .-% of a solvent mixture of methyl ethyl ketone and propylene glycol monomethyl ether (40/60).
• Mw molecular weight
• the copy varnish film is dried at 125 ° C for one minute.
• the film weight is 1 to 3 g / m2, in particular 2.4 g / m2.
• the presensitized planographic printing plates are processed into printing forms.
• the plates are contacted in a vacuum contact copier frame by evacuation with a test pattern, exposed with a 5 kW metal halide-doped mercury vapor lamp at a distance of 110 cm so that an open step 4 results in the UGRA offset test wedge after development, which leads to high exposure Film edge removal corresponds.
• the copy varnish solution contains the following components: 4.80% by weight cresol-formaldehyde novolak resin with a hydroxyl number of 420 according to DIN 53783/53240 and a molecular weight (Mw) according to GPC of 10,000 (polystyrene standard), 1.05% by weight of the esterification product of 3 mol of 1,2-naphthoquinone-2-diazide-4-sulfonyl chloride and 1 mol of 2,3,4-trihydroxybenzophenone, 0.05% by weight of 2- (4-styrylphenyl) -4,6-bis-trichloromethyl-s-triazine, 0.10% by weight crystal violet (CI 42555) and 1.00% by weight of silica filler with an average grain size of 3.9 ⁇ m, 0.10% by weight of surfactant based on dimethylsiloxane and ethylene oxide units, ad 100 wt .-% of a solvent mixture of te
• the copy lacquer film is dried at 125 ° C. for 1 minute.
• the film weight is 1.8 g / m2.
• a potassium silicate developer according to DE-A 40 27 299 with a total alkali content of 1.3 mol / l and a content of polyglycol-1000-dicarboxylic acid of 0.6% by weight is used for the development.
• the copying behavior i.e. light sensitivity, reproduction, color fog, susceptibility to under-radiation
• the printing behavior ie free running, water requirement, support
• the solution contains the following components: 3.00% by weight trimethylolpropane triacrylate, 10.00% by weight copolymer of methyl methacrylate and methacrylic acid with an acid number of 190 and a molecular weight (Mw) according to GPC of 50,000 (polystyrene standard), 0.05% by weight of dibenzalacetone, 0.05% by weight of 9-phenylacridine, 0.10% by weight of an azo dye composed of 2,4-dinitro6-chlorobenzenediazonium chloride and 2-methoxy-5-acetylamino-N-cyanoethyl-N-hydroxyethyl-aniline and ad 100 wt .-% ethylene glycol monomethyl ether.
• Mw molecular weight
• the copy lacquer film is dried for two minutes at 125 ° C. and has a layer weight of 3.0 g / m2.
• the barrier layer After drying for 1 minute at 125 ° C, the barrier layer has a layer weight of 2.0 g / m2.
• the presensitized planographic printing plates thus obtained are exposed as in the examples in item 1) for 35 s and then in a developing device as in the examples in item 1) with an upstream demineralized water rinse of the front to remove the PVAl cover layer at a processing speed of 0.6 m / min in a potassium silicate developer with a total alkali content of 0.55 mol / l and a non-ionic wetting agent content (coconut fatty alcohol polyoxyethylene ether with approx. 8 oxyethylene units (Genapol C080 from Hoechst AG)) of 1 g / l .
• the oxide degradation is again evaluated as in the examples under point 1).
• a developer exhaustion test is carried out with a number of settings up to a load of 3 m 2 printing plates / 1 l developer.
• Comparative Example 3-7 a thick and then 3-8 light coating on the squeeze rollers is shown, while in Example 3-3 no coating is visible.
• the coating solution contains the following components: 5.00% by weight of 2,5-bis (4'-diethylaminophenyl) -1,3,4-oxadiazole, 5.00% by weight cresol-formaldehyde novolak resin (corresponding to Examples 1), 0.01% by weight of rhodamine FB (CI 45170) and ad 100 wt .-% ethylene glycol monomethyl ether.
• the layers are dried at 125 ° C. for two minutes and have a layer weight of 5 g / m2.
• planographic printing plates made in this way which work according to the electrophotographic principle, are charged in the dark with a corona to -500 V, exposed in projection with 8 halogen lamps with 500 watts each for 30 s.
• the resulting latent charge image is emphasized with the aid of a magnetic roller with a commercially available toner / carrier mixture.
• the non-image areas are removed with the following solution: Na2SiO3 2.0% by weight NaOH 0.2% by weight Ethylene glycol 15.0% by weight n-propanol 10.0% by weight

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Photosensitive Polymer And Photoresist Processing (AREA)
• Printing Plates And Materials Therefor (AREA)
• Materials For Photolithography (AREA)

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Cited By (49)

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• 1991
  • 1991-10-16 DE DE4134143A patent/DE4134143A1/de not_active Withdrawn
• 1992
  • 1992-09-28 US US07/952,092 patent/US5314787A/en not_active Expired - Fee Related
  • 1992-10-09 DE DE59207665T patent/DE59207665D1/de not_active Expired - Fee Related
  • 1992-10-09 EP EP92117258A patent/EP0537633B1/fr not_active Expired - Lifetime
  • 1992-10-15 JP JP4277432A patent/JPH05221178A/ja active Pending

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